Test more than the midpoint

Suppose a caliper used for cosmetic packaging reads calibrated references of 10.00, 15.00 and 20.00 mm as 10.05, 15.00 and 19.94 mm, respectively. These are hypothetical averages. The offsets are +0.05, 0.00 and −0.06 mm. The midpoint check would miss the change in bias across the range.

Packaging sample showroom of SamBound New Material Technology Company Ltd. (sambound.com).

Compare offsets at the sizes you use

Select calibrated references that span the working range and use the same contact mode as the production measurement. Repeat readings at each point. Plot the average bias against reference size and consider the repeat scatter and reference uncertainty when judging whether the differences matter. A roughly constant offset and a bias that changes with size call for different investigations.

These checks cover the tested range and setup. Changes in jaw geometry, contact force or part compliance may matter when moving from reference artifacts to molded packages.

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